The present invention relates to an elastic flat tread for an endless crawler belt, which is used for a hydraulic shovel, bulldozer, and other construction equipment, and particularly, to an elastic flat tread with improvements in the shapes and the materials of a core and an elastic solid covering the core.
Conventional construction equipment such as hydraulic shovels and bulldozers with steel crawler belts being, attached has the disadvantage of damaging asphalt road surfaces when traveling on a public road on the move between work sites, and therefore increasing number of vehicles are equipped with rubber crawler belts recently.
The rubber crawler belts are formed by a number of core wires and cores embedded in rubber in an endless shape, but if problems such as a crack and peeling, of rubber occurs, it is difficult to repair them, which necessitates the replacement of the crawler belt to a new one, thereby causing the disadvantage of increasing user cost.
In order to overcome the foregoing disadvantage, elastic flat treads formed by iron crawler plates with elastic solids such as rubber being bonded thereto are used. Recently, an art is developed, in which a core is embedded into an elastic solid to construct an elastic flat tread, a plurality of which are disposed in a longitudinal direction of a crawler to thereby form an endless crawler belt.
As a prior art of an elastic flat tread, for example, Japanese Patent Application Laid-open No. 7-152305 is known, which will be explained with reference to FIG. 53 and FIG. 54. In an elastic flat tread 140, a planar core 120 is covered with an elastic solid 130 from the entire ground-contacting side toward core end portions 121 and 121 in a longitudinal direction of the core 120 on the side not in contact with the ground, and bonded thereto by vulcanization. The core 120 is fastened to a link 150 by bolts not illustrated. Numeral 132 is a bolt hole for insertion of the bolt.
However, in the above elastic flat tread 140, as shown in FIG. 55, elastic solid end portions 131 are locally bent to thereby cause the concentration of stress, when the elastic flat tread 140 runs on a protruding object such as a rock or stone A and a curb stone of a sidewalk not illustrated. As a result, the disadvantage of a crack P occurring in the elastic solid end portion 131 is caused. This is because the core 120 is designed to have high rigidity so as not to be deformed even if the vehicle weight W of construction equipment is exerted on the elastic flat tread 140 via a lower roller 145 and a link 150.
Meanwhile, even the elastic solid 130 with higher rigidity in nature has lower rigidity than that of the core 120. Consequently, when running on a protruding object such as a rock or stone A and a curb stone of a side walk, so long as the protruding object does not escape therefrom, distortion concentrates on the elastic solid 130 due to the difference in rigidity between the core 120 and the elastic solid 130, thereby causing the crack P in the elastic solid end portion 131 shown in FIG. 55.
Further, the head portions of bolts fastening the core 120 and the link 150 contact the elastic solid 130, thus causing the disadvantage that a crack and peeling occur at the bolt insertion holes 132.
The present invention is made in view of the disadvantages of the prior art, and its object is to provide an elastic flat tread capable of preventing an elastic solid from cracking when a vehicle runs on or collides with a rock or a stone, or a curb stone of a sidewalk during traveling.
In order to attain the above object, a first aspect of an elastic flat tread according to the present invention is an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, and characterized in that
the aforesaid core is any core of a core attached to the aforesaid link and a core attached to a metal plate which is attached to the aforesaid link, and in that
end portions in a longitudinal direction of the aforesaid any core are bent toward the side not in contact with the ground.
According to the above structure, even if the vehicle runs on or collides with a protruding object such as a rock or stone, or a curb stone of a sidewalk, since the end portions in a longitudinal direction of the core are bent toward the side not in contact with the ground, the rock or stone escapes from the elastic solid end portion formed along the bent portion of the core, thus making it possible to avoid local concentration of stress on the elastic solid. When the angle of bend of the core end portion is made larger, even if the elastic solid end portion formed along the bent portion collides with a curb stone of a sidewalk, local concentration of stress on the elastic solid can be avoided. The angle of bend of core end portion is appropriately set in the range of 10 degrees to 90 degrees, and the angle of bend of the core end portion is set in consideration of the weights of various kinds of models small to large in size, the sizes of the elastic flat treads, the lengths in the longitudinal direction of the cores, and the like. For example, in a small-sized model which frequently operates in a working site with many small rocks and stones, the angle of bend of the core end portion may be made smaller, and in a large-sized model which frequently operates in a working site with many large rocks and stones, the angle of bent of the core end portion may be larger. Consequently, even if the vehicle runs on a protruding object such as a rock or stone, or a curb stone of a sidewalk during traveling, a crack does not occur in the elastic solid end portion, thus increasing durability of the elastic flat tread.
A second aspect of the invention is characterized in that at least one layer of cable layers is provided inside the aforesaid elastic solid, under the aforesaid any core, near an end portion in a longitudinal direction of the aforesaid any core, in the structure of the first aspect of the invention.
According to the above structure, in addition to the operational effects of the first aspect of the invention, the cable layer is embedded near the end portion in a longitudinal direction of the core, thereby increasing the rigidity at this portion, which eliminates the occurrence of a crack in the elastic solid even if the elastic solid end portion runs on or collides with an protruding object such as a rock or stone, or a curb stone of a sidewalk. Consequently, durability of the elastic flat tread is improved, which makes the elastic flat tread useful to construction equipment operating in various working sites.
A third aspect of the invention is characterized in that a direction in which cable wires of the aforesaid cable layers are placed is either one of the parallel and diagonal directions relative to the longitudinal direction of the aforesaid any core, or the combination of two directions or more selected from the parallel and diagonal directions, in the structure of the second aspect of the invention.
According to the above structure, the elastic solid is strengthened by the cable layer with the direction of the cable wires being either one of or two or more of the parallel and diagonal directions relative to the longitudinal direction of the core, and therefore a crack does not occur in the elastic solid even if the elastic solid end portion runs on or collides with a protruding object such as a rock or stone, or a curb stone of a sidewalk. Consequently, durability of the elastic flat tread is improved, which makes the elastic flat tread useful to construction equipment operating in various working sites.
A fourth aspect of the invention is characterized by including a synthetic resin member which is placed near the end portion in the longitudinal direction of the aforesaid any core, and which is fixed to the aforesaid elastic solid, in the structure of the first aspect of the invention.
According to the above structure, if the synthetic resin member with a smaller friction coefficient is fixed to the elastic solid, a rock or a stone slips and escapes, even if the synthetic resin member runs on a protruding object such as a rock or stone, or a curb stone of a sidewalk, thereby making it possible to avoid local concentration of stress. Further, by using the synthetic resin member with higher rigidity than the elastic solid, rigidity around the core end portion can be increased. Consequently, even if the elastic flat tread runs on a protruding object such as a rock or a stone, or a curb stone of a sidewalk during traveling, a crack does not occur, thus improving durability of the elastic flat tread.
A fifth aspect of the invention is characterized in that the aforesaid elastic solid is integrally formed by elastic solids with different hardnesses, in which the hardness at a portion in contact with the aforesaid any core is the highest and the hardness sequentially lowers toward the ground-contacting side, in the structure of the first aspect of the invention.
According to the aforesaid structure, in addition to the operational effects of the fist aspect of the invention, the elastic solid with a higher hardness is strong against an unbalanced load caused by deflection or the like, but provides poor riding quality and less wear resistance on the other hand, and thus the elastic solid is designed to have the highest hardness at the portion nearest to the core. To make the hardness sequentially lower toward the ground-contacting side, the elastic solid having a lower hardness is provided on the ground-contacting side in consideration of riding quality and wear resistance. Accordingly, even if the elastic solid end portion runs on a protruding object such as a rock or stone, or a curb stone of a sidewalk, a crack does not occur in the elastic solid end portion, thus improving durability of the elastic flat tread.
A sixth aspect of the invention is characterized in that the aforesaid any core is formed of spring steel, in the structure of the first aspect of the invention.
According to the above structure, as in the structure of the first aspect of the invention, the end portions in the longitudinal direction of the core formed of spring steel are bent toward the side not in contact with the ground, and therefore even if the elastic solid end portion formed along the bent portion of the core runs on a protruding object such as a rock or stone, or a curb stone of a sidewalk, the core formed of spring steel is displaced upward, thereby making it possible to avoid local concentration of stress on the elastic solid end portion. Consequently, even if the elastic solid end portion runs on a protruding object such as a rock or stone, or a curb stone of a sidewalk, a crack does not occur, thus improving durability of the elastic flat tread.
A seventh aspect of the invention is characterized in that the ratio between a height h, which is from a mounting surface for the aforesaid link up to a tip end in a height direction of the end portion in the longitudinal direction of the aforesaid any core, and a link pitch Lp is 0.05xe2x89xa6h/Lpxe2x89xa60.25, in the structure of the first aspect of the invention.
An eighth aspect of the invention is characterized in that the ratio between a height h, which is from a mounting surface for the aforesaid link up to a tip end in a height direction of the end portion in the longitudinal direction of the aforesaid any core, and a height H of the elastic flat tread is 0.08xe2x89xa6h/Hxe2x89xa60.50, in the structure of the first aspect of the invention.
A ninth aspect of the invention is characterized in that the ratio between a width W1 of the aforesaid any core, and a width W2 of a tip end in the longitudinal direction of the aforesaid any core is 0.5 less than W2/W1xe2x89xa60.9, in the structure of the first aspect of the invention.
In the above seventh aspect through the ninth aspect of the invention, the dimensional ratio of the core and the like of the first aspect of the invention is specified, and as in the operational effects of the first aspect of the invention, a crack does not occur in the elastic solid end portion, thus improving durability of the elastic flat tread.
A tenth aspect of the invention is, in an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, characterized in that
the aforesaid core is any core of a core attached to the aforesaid link and a core attached to a metal plate which is attached to the aforesaid link, and is characterized in that
at least one layer of cable layers is provided inside the aforesaid elastic solid, under the aforesaid any core, near an end portion in a longitudinal direction of the aforesaid any core.
The above structure corresponds to the structure of the second aspect of the invention of which core is not bent, and thus the same operational effect as in the second aspect of the invention can be obtained.
An eleventh aspect of the invention is characterized in that a direction in which cable wires of the aforesaid cable layers are placed is either one of the parallel and diagonal directions relative to the longitudinal direction of the aforesaid any core, or the combination of two directions or more selected from the parallel and diagonal directions, in the structure of the tenth aspect of the invention.
The above structure corresponds to the structure of the third aspect of the invention, and the same operational effects as in the third invention can be obtained.
A twelfth aspect of the invention is, in an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, is characterized in that
the aforesaid core is any core of a core attached to. the aforesaid link and a core attached to a metal plate which is attached to the aforesaid link, and characterized by further including
a synthetic resin member placed near an end portion in a longitudinal direction of the aforesaid any core and fixed to the aforesaid elastic solid.
The above structure corresponds to the structure of the fourth aspect of the invention of which core is not bent, and thus the same operational effects as in the fourth invention can be obtained.
A thirteenth aspect of the invention is, in an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, characterized in that
the aforesaid core is any core of a core attached to the aforesaid link and a core attached to a metal plate which is attached to the aforesaid link, and characterized in that
the aforesaid elastic solid is integrally formed by elastic solids with different hardness, in which the hardness at a portion in contact with the aforesaid any core is the highest and the hardness sequentially lowers toward the ground-contacting side.
The above structure corresponds to the structure of the fifth aspect of the invention of which core is not bent, and thus the same operational effects as in the fifth aspect of the invention can be obtained.
A fourteenth aspect of the invention is, in an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, and is characterized in that
the aforesaid core is any core of a core attached to the aforesaid link and a core attached to a metal plate which is attached to the aforesaid link, and characterized in that
the aforesaid any core is formed of spring steel.
The above structure corresponds to the structure of the sixth aspect of the invention of which core is not bent, and the same operational effects can be obtained as in the sixth aspect of the invention.
A fifteenth aspect of the invention is, in an elastic flat tread having links of which end portions are connected to the adjacent end portions in a traveling direction of a crawler with a pin, and a core covered with an elastic solid at least on the ground-contacting side, characterized in that
end portions in a longitudinal direction of the aforesaid core are bent toward the side not in contact with the ground, and characterized in that
end portions of the aforesaid elastic solid are protruded outward relative to the tip ends of the end portions in the longitudinal direction of the aforesaid core.
According to the above structure, when the vehicle runs on or collides with a protruding object such as a rock or stone, or a curb stone of a sidewalk during traveling, the end portion in the longitudinal direction of the core is bent toward the side not in contact with the ground, thus making it possible to avoid local concentration of stress on the elastic solid as a result that the rock or the stone escapes from the elastic solid end portion formed along the bent portion of the core. Since the elastic solid end portion formed along the bent portion of the core is protruded outward from the end portion of the core, therefore in the elastic solid end portion, an impact caused by the collision with an protruding object such as a rock or stone, or a curb stone of a sidewalk can be lessened. Accordingly, even if the vehicle runs on or collides with a protruding objet such as a rock or stone, or a curb stone of a sidewalk during traveling, a crack does not occur in the elastic solid end portion, thus improving durability of the elastic flat tread.